Okay, but inside of Apache's httpd.conf configuration file (or perhaps an included .conf file), there should be some modifications that integrate PHP with Apache; otherwise, how will Apache know that .php files are to be handled by the PHP interpreter?
If you're getting file download requests for .php files, then it sounds like Apache wasn't properly configured to pass such requests on to the PHP interpreter. The PHP manual page [man]install.windows.apache2[/man] talks about how to configure Apache to do so.